There is a great need for testing and monitoring the operation of electrical-mechanical components of systems. For corporations that produce systems with electrical-mechanical components, it is necessary to test the manufactured systems for defects before shipping the systems to customers, thereby increasing profitability and customer satisfaction. The industries that utilize these electrical-mechanical components want to minimize machine down time for their customers. Having devices and systems that can characterize the operation of the electrical-mechanical components, and then identify and report causes of failure, can reduce the amount of machine down time for the customer and enhance the profitability of the corporation which produced the systems and the customer using the systems. The vast importance of quality control cannot be overstated.
Many devices and systems today include a large number of electrical-mechanical components that require testing and monitoring. For instance, large library data storage systems include a variety of servo-mechanisms, DC-servo motors, and solenoids. Similarly, modern automobiles use a variety of electrical-mechanical components to operate the various features of an automobile such as power mirrors, power door locks, power track release, and a retractable radio antenna. In many cases, all of the electrical-mechanical components are connected to a single power supply. Alternatively, multiple power supplies are used to provide power for multiple electrical-mechanical components individually, or in groups. Connecting test equipment for each and every single electrical-mechanical component when a system failure occurs is a time consuming and hence costly procedure for a customer engineer. It is highly desirable to develop a method and system than can test the function of multiple electrical-mechanical components simultaneously without having to instrument and test each device individually
There are numerous systems and devices known in the current state of the art that address the need to test and monitor electrical-mechanical components. U.S. Pat. No. 5,629,870 entitled “Method and Apparatus for Predicting Electric Induction Machine Failure During Operation” discloses one such testing and monitoring system for induction motors. This patent teaches a method and apparatus for identifying in real time an operating condition of an in-service induction motor, which draws a power load, by monitoring the frequency content of the power signature and associating the frequency components with device operating conditions. The method and apparatus taught by the '870 patent uses a data conditioning sampler to monitor and sample the current used by the induction motor. The patent describes that each induction motor has a separate control transformer. The patent goes on to disclose that a data conditioning sampler is coupled to each respective control transformer to sample the induction motor current. Alternatively, the patent teaches that a multiplexer could be used to enable one data conditioning sampler to interact with multiple control transformers and sample induction motor current.
The data gathered by the data conditioning sampler is in the time domain. An electrical device, referred to in the patent as a preprocessor, converts the time domain data gathered by the data conditioning sampler into the frequency domain by performing a Fast Fourier Transform (FFT) on the data. A filter, referred to as a spectral characteristic component selector filter, selects for analysis at least one specific frequency by referencing a database containing typical operational frequencies of the motor. A neural network then associates the selected frequency with an operating condition of the motor. An additional processor may then enunciate the association to a user via an output device. In addition, this processor may generate a control signal to operate an electrical distribution system protection or a control apparatus.
Another system to monitor the performance of electrical motors is taught by U.S. Pat. No. 5,689,194 entitled “Acoustic Motor Current Signature Analysis System with Audio Amplified Speaker Output.” This patent essentially teaches a system that converts a noise portion of the motor current signal into an audio signal within an audible frequency range. The patent discloses that the system has an input for receiving a motor current noise signal. A demodulator then demodulates the motor current noise signal. A signal conditioner filters the noise signal selecting predetermined frequencies of the motor current noise and removing unwanted frequencies and harmonics from the motor current noise signal. A signal translator shifts the selected frequencies of the motor current noise signal into an audio bandwidth. An audio section having an amplifier and a speaker coupled to the amplifier amplifies and plays the selected frequencies of the motor current noise signal.
Both of the U.S. Pat. Nos. 5,629,870 and 5,689,194 discussed above teach testing and monitoring systems that are directed solely towards induction motors. However, a great deal of modern equipment uses electrical-mechanical devices other than just induction motors. For instance, large library data storage systems include numerous servo-mechanisms that also require monitoring. Many systems use solenoids. It is highly desirable to have a testing and monitoring system that can function for devices other than just induction motors. In addition, U.S. Pat. No. 5,629,870 teaches an induction motor monitoring system that monitors each motor individually by sampling current data from each individual motor. It is highly desirable to develop a system that can monitor systems of multiple interconnected electrical-mechanical devices by sampling current data from a single node in the system instead of from each individual device.
Other devices and systems used to test electrical equipment are currently known in the art. A system for testing integrated circuits is disclosed in U.S. Pat. No. 4,763,066 entitled “Automatic Test Equipment for Integrated Circuits.” The apparatus taught by this patent includes a semiconductor tester that produces an analog signature signal relative to a circuit node of an electronic circuit, such as a pin connection of an integrated circuit. The analog signature signal is the result of horizontal and vertical signals that are also directed to an integrator/A-D converter. The integrator/A-D converter produces therefrom a set of four digital signals representing said analog signature. These digital signals are then compared in a computer against reference digital values for the same circuit node of the same electronic circuit that is known to be good. If the digital signals are not within a selected range relative to the reference digital values, the analog signature of the circuit node is displayed for inspection and evaluation by an operator.